(CNN) -- The full-body scanning technology being adopted and discussed since the attempt to take down a passenger plane on Christmas Day isn't a "magic machine" that will solve aviation security issues, experts say.

"Regardless of the sophistication of the piece of technology, if you can collect the information on how it works and what its technical parameters are, then that machine is not going to deter a [sophisticated] terrorist operation," said Dr. Richard Bloom, director of terrorism, intelligence and security studies at Embry-Riddle Aeronautical University.

Full-body screening and other security measures are more effective in detecting threats from an increasing number of unsophisticated, mentally troubled suspects acting alone, he said. The technology is "only a piece" of aviation security.

"If you know ahead of time what you're going to be facing, you either plan to beat it, or you go somewhere else," Bloom said.

The advanced imaging scanners would not have caught substances hidden in a bodily orifice or substances concealed by folds of skin on an obese suspect, he added.

Security technologist Bruce Schneier believes that the body scanning machines are a waste of money. Investigation and intelligence gathering is where the money would make a difference, he said.

"Stop trying to guess. You take away guns and bombs, the terrorists use box cutters. You take away box cutters, they put explosives in their shoes. You screen shoes, they use liquids. You take away liquids, they strap explosives to their body. You use full-body scanners, they're going to do something else," said Schneier, who is the author of a number of security-related books, including "Beyond Fear."

Federal authorities have charged Umar Farouk AbdulMutallab, 23, of Nigeria with trying to detonate explosives hidden in his underwear on a flight from Amsterdam, Netherlands, to Detroit, Michigan. The device failed to fully detonate.

In Amsterdam, metal detectors and X-ray machines were in place, but the advanced scanning technology was not available. Dutch authorities have said they are confident about how AbdulMutallab was screened but acknowledge that they could not have detected the explosive material that he was said to be carrying.

Amsterdam's Schiphol Airport will begin using the full-body scanners on all passengers taking flights to the United States, the Dutch interior minister said Wednesday. Also Wednesday, the airport authority in Nigeria, where AbdulMutallab's flight to Amsterdam originated, announced plans to add body scanners to its security system.

In the United States, 40 of these advanced imaging machines are in use in 19 airports, according to the TSA. Only in six airports are they used as a primary screening option.

An additional 150 advanced imaging machines will be installed in U.S. airports over the next year, and the TSA plans to purchase 300 more machines in 2010, the TSA's Soule said.

The controversial technology, first used in a U.S. airport in 2007, can find hidden objects that metal detectors can't.

"Advanced imaging technology enhances security by safely screening passengers for metallic and non-metallic threats including weapons, explosives and other objects concealed under layers of clothing without physical contact," Soule said.

Privacy rights groups are wary of movements to impose the anatomically revealing technology on all travelers as a primary screening method.

"Obviously, we have a concern, because it's a virtual strip search that is terribly invasive," said Michael German, policy counsel for the American Civil Liberties Union.

The Electronic Privacy Information Center, a Washington-based public interest research center, filed a lawsuit in November against the Department of Homeland Security seeking details under the Freedom of Information Act about the department's use of the advanced imaging technology.

The privacy rights group is concerned that the focus on hidden explosives will push the TSA to ramp up use of the machines as a primary screening tool without resolving concerns about appropriate use of the technology, said associate director Lillie Coney.

Addressing privacy concerns, the TSA says faces are blurred on the body scans generated by the agency's machines. Agents who deal directly with passengers do not see the scans, and the agents who review the scans do not see the passengers.

Because only a handful of the machines currently are in use in the U.S. as a primary screening measure and only a few other countries are using the technology, most travelers flagged for secondary screening would encounter other means of detecting threats, including pat-down searches and technology that can detect traces of explosives.

Some security analysts say pat-down searches -- which are often perfunctory -- are useless.

"Basically, any pat-down that you are not violated and embarrassed after is ineffective," Schneier said.

In April 2008, the TSA announced an "enhanced pat-down search" to address items that could be hidden in "sensitive areas of the body," including the chest and groin. The more thorough searches, the announcement said, would be used only when all other screening measures failed to resolve a security alarm.

The agency said Wednesday that this is not the current procedure but declined to offer further details on how pat-down guidelines have evolved.

A separate technology that analyzes samples for traces of explosive material is in place at every airport, Soule said. More than 7,000 explosives trace detectors are in use in airports across the country.

Screening procedures and technology constitute only one layer in combating terrorism, Bloom said. There is no "magic machine" or "magic technology."

"Security has to be layered and the layering has much more to do than pat downs and technology, it also includes collecting intelligence, analyzing it and transmitting it in a prompt and responsive and secure fashion," he said.

"In general, the odds are really stacked in the terrorists' favor ... because they only have to be successful one time and the government has to be successful all the time."